The present invention concerns a device and a method for an authorization interrogation in a motor vehicle.
The article xe2x80x9cKeyless entry system with radio car transponderxe2x80x9d, by Motoki Hirano, Mikio Takeuchi, Takahisa Tomoda, Kin-Ichiro Nakano, published in the IEEE transactions on industrial electronics, Vol. 35, No. 2, May 1988, pages 208 through 216, describes a keyless entry system. In this system, a transponder carried by the user executes an access authorization dialog with an antenna arranged in the vehicle. An access authorization being or not being granted is based on the access authorization dialog. The antennas of the vehicle are arranged in the lateral rearview mirror housing and in the rear bumper.
However, this antenna array results in an increased cabling outlay since provision must be made for a data connection to the door controller generally arranged in the passenger compartment. The accommodation in the exterior mirror allows the external space to be interrogated without greater attenuation of the magnetic field.
An object of an exemplary embodiment of the present invention is directed to conveniently arranging an antenna only in the interior space and, at the same time, ensuring a trouble-free signal exchange with the transponder.
A device and/or method according to an exemplary embodiment and/or exemplary method of the present invention concerning an authorization interrogation system in a motor vehicle may have a transponder which exchanges data with an antenna array within the framework of an authorization interrogation. The antenna array can be composed of a left antenna array arranged on the left side of the motor vehicle and of a right antenna array arranged on the right side of the motor vehicle. During an external space interrogation, the left antenna array receives a current for the external space interrogation and the right antenna array receives a current for the external space interrogation. The currents of the left and of the right antenna arrays can be selected to have different magnitudes, to be different from zero and/or to have current phases selected to be inverted relative to each other. The antenna arrays can be accommodated in the lateral posts behind the right or left side-doors, respectively. Due to the spatial proximity of the antenna array to the vehicle locking system, the cabling outlay can be reduced. The different selection of the current magnitude or of the current phases (inverting control) of the left and right antenna arrays can contribute to an unequivocal transponder recognition on one of the two (right or left) sides of the motor vehicle. If, for example, the left external space of the motor vehicle is to be interrogated, a correspondingly high current is applied to the left antenna array. The left antenna array ensures the communication with the transponder, which is generally located on the left side. The right antenna array can be controlled using a lower current in an inverting manner with respect to the useful signal of the current of the left antenna array to compensate for the field which is radiated by the left antenna array toward the right side. This can be done in such a manner that a transponder possibly located on the right side of the vehicle cannot enter into a signal exchange with the base station. In this manner, manipulations can be reduced. Moreover, an unwanted communication of a transponder located on the left side with the right antenna array can be prevented as well. Because of the possibility of this active disturbance field compensation, the transmitting power of the antenna which interrogates the desired side area can be increased. The disadvantageous effects due to the unwanted emergence of the magnetic waves on the opposite vehicle side do not impair the reliability of the authorization interrogation.
In another exemplary embodiment of the present invention, an antenna can be provided in the antenna array to be used both for the external space interrogation and for an interior space interrogation. Due to this double use, the required component outlay is reduced. The interior space interrogation can be carried out for a driving authorization interrogation. The control of the left and right antenna arrays can be selected in such a manner that each one covers a half-space of the passenger compartment for transponder communication. For interior space monitoring, the two antenna arrays can be controlled successively. That is, each of the antenna arrays can cover the whole interior space.
In another exemplary embodiment of the present invention, the antenna array can be composed of at least two antennas which are aligned orthogonally relative to each other. In this manner, a rotating magnetic field can be generated so that a signal exchange with a transponder located in any arbitrary position is achieved.
The antenna used both for the interior space interrogation and for the external space interrogation is preferably designed as a ferrite coil or an air coil. In this manner, the magnetic fields needed for a reliable data exchange can be attained.
Another exemplary embodiment of the device and/or method according to the present invention for an authorization interrogation in a motor vehicle first queries an operating signal. Then, a current value for controlling an antenna array is selected as a function of the operating signal. Then, the antenna array is controlled using the selected current value for carrying out the authorization interrogation. A desired interrogation type, external space interrogation as access authorization, and interior space interrogation as driving authorization, can be allocated in a simple manner on the basis of the operating signals.